Florida Drinking Water Operator "B" Practice Test

What is the main instrument used in threshold odor number analysis?

1. Gas chromatography

2. Field olfactometer

3. The human nose

4. Spectrophotometer

The correct answer is: The human nose

In threshold odor number analysis, the primary instrument utilized is the human nose. This method involves a sensory evaluation where trained panelists detect and record odors at various dilutions. The threshold odor number, which indicates the level at which a specific odor can be detected, is determined based on this sensory response. Using the human nose allows for direct perception and qualitative assessment of odors that may not be quantified by mechanical devices. In practice, panelists are exposed to samples that are systematically diluted until they can just barely perceive the odor. This human-based approach is vital because it reflects the actual experience of individuals who will encounter the odors in their environment. The other choices serve different functions. Gas chromatography, for example, is a technique used to separate and analyze compounds but does not measure odor perception directly. A field olfactometer can be used to measure odor concentrations in a more structured manner but still relies on human sensory evaluation for threshold determinations. Lastly, a spectrophotometer measures light absorption but is not capable of assessing odor. Therefore, the human nose remains the fundamental instrument for determining threshold odor numbers through subjective olfactory responses.